Evaluation of biopesticides in control of red spider mites (tetranychus evansiy on tomatoes (lycopersicum esculentum)
Three neem-based biopesticides, namely Achook (0.15% Azadirachtin), Neemroc (0.03% Azadirachtin + 32% neem oil) and Neem + Corn (0.03% Azadirachtin + 32% corn oil) and one garlic-based product, namely GC- mite (40% garlic extract), were evaluated under laboratory, greenhouse and field conditions for their efficacy against red spider mites (Tetranychus evansi Baker and Pritchard) on tomatoes (Lycopersicum esculentum L.). A synthetic acaricide, namely Omite (57% propargite) was also used as a psitive control. For concentration-mortality bioassays, tomato leaf discs were dipped into four different concentrations of the biopesticides, placed on moist cotton wool in petridishes and 15 adult female mites introduced to each disc after one hour. The mortality after 96 hours was low in all biopesticide treatments with the highest value recorded being 53% for Neem + Corn (25ml/l) followed by Neemroc (25ml/l) with 49% mortality. GC- mite (20 mlll) caused 38% and Achook (2.5 ml/l) 34% mortality. The synthetic acaricide, Omite (2.0mlll) caused 100% mortality. All the biopesticides and the synthetic acaricide showed strong repellent effect, ranging from 76% to 96% within 6 hours. Mortality resulting from 1 hour residual effect of biopesticides was very low, the highest being only 15 % caused by Achook, compared to 100% caused by the synthetic acaricide, Omite. High mortalities of adults and larvae resulting from contact effect of the biopesticides were observed in all biopesticides except Achook. Achook caused low deaths. Neem + Com caused 92% mortality, followed by Neemroc (54%), GC- mite (54%) and Achook (33%) mortality of adult female mites at 96 hours. The larvae mortality was higher than that of the adult for the GC- mite (85%) and Neemroc (72%) but lower for Neem + Corn (82%). Achook caused about the same mortality oflarvae as of adults (35%). Greenhouse and field experiments showed Neernroc and Neem + Com to be more effective in control of T evansi than Achook and GC- mite, although not as much as the Omite. There were no significant differences in yields observed in all the treatments in both greenhouse and the field experiments carried out in this study. The potential of using Neernroc and Neem + Com formulations in the control of spider mites on tomatoes is evident in this study. Although not as effective as the synthetic acaricide, the biopesticides can be included in the modem pest management programmes where use of synthetic pesticides is not required or is restricted.